1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus, and particularly relates to an X-ray diagnostic apparatus in which an X-ray generating portion and an X-ray detecting portion are respectively independently arranged and can instantly cope with pickup images (fluoroscopy, radiography) in an over-table tube and an under-table tube and pickup images in various positionings.
2. Prior Art
In a holding device for a circulatory organ as a conventional X-ray diagnostic apparatus, an X-ray generating portion and an X-ray detecting portion are oppositely arranged in both end portions of an arm and are fixedly held. It is known that an arm shape is generally divided into a "C-type" having approximately a C-character shape and a "U-type" having approximately a U-character shape. However, in view of efficiency of three dimensional positioning, the C-type arm is arranged in many cases at present.
FIG.1 shows a perspective view of the holding device for a circulatory organ having this C-type arm.
As shown in FIG. 1, the holding device for a circulatory organ has a rail holding portion 100, a stay portion 101, a holder 102 and a C-type arm 103. The rail holding portion 100 movably holds the holding device for a circulatory organ along a rail attached to a ceiling. The stay portion 101 is rotatably suspended from this rail holding portion 100. The holder 102 is so held on a side of this stay portion 101 opposed to the rail holding portion 100 as to rotate about a main shaft. The C-type arm 103 is slidably held by this holder 102.
An X-ray generating portion 104 and an X-ray detecting portion 105 (an image intensifier, an optical system, a TV camera, etc.) are so arranged in both end portions of the C-type arm 103 as to be opposed to each other. The X-ray detecting portion 105 is so controlled by a moving mechanism 106 as to move upward and downward (toward the X-ray generating portion 104 and the opposite direction).
In such a holding device for a circulatory organ, the X-ray generating portion 104 and the X-ray detecting portion 105 arranged in both end portions of the C-type arm 103 are heavy in weight and large in size. Further, the C-type arm 103 has an asymmetrical shape. Accordingly, it is difficult to rotationally balance the C-type arm 103 in slide motion, main shaft rotation motion, etc. Therefore, positioning control of the C-type arm 103 is electrically performed by operating a dedicated handle, a joy stick, etc.
In contrast to this, separated holding devices generally called BC arms are known. In this separated holding devices, the X-ray generating portion and the X-ray detecting portion are separately held and are oppositely arranged. FIG.2A shows the constitution of the separated holding devices called the BC arms.
In FIG. 2A, the BC arms have a rail holding portion 120 and an elastic arm 121. The rail holding portion 120 can move the X-ray generating portion 124 along a rail attached to a ceiling. One end of the elastic arm 121 is so held by the rail holding portion 120 as to freely extend and contract. The X-ray generating portion 124 is arranged at the other end of the elastic arm 121. The BC arms also has a rail holding portion 122 and an elastic arm 123. The rail holding portion 122 can move the X-ray detecting portion 125 along the rail attached to the ceiling, independently to the movement of the X-ray generating portion 124. One end of the elastic arm 123 is so held by the rail holding portion 122 as to freely extend and contract. The X-ray detecting portion 125 is arranged at the other end of the elastic arm 123.
In such separated holding devices, only an oscillating movement, a horizontal movement and a vertical movement of the X-ray generating portion 124 (or the X-ray detecting portion 125) can be made. Accordingly, as shown in FIG. 3, the separated holding devices are mainly used for a lateral radiography as a lateral positioner of a biplane radiography.
FIG. 2B is a view showing a U-type arm as another positioner for biplane radiography.
In FIG. 2B, the U-type arm has a stay portion 110 and a U-type arm 111. The stay portion 110 is held by a rail holding portion for movably holding the U-type arm along a rail attached to a ceiling. The U-type arm 111 is so held on the side of the stay portion 110 opposed to the rail holding portion as to rotate about a main shaft 127. An X-ray generating portion 112 and an X-ray detecting portion 113 are oppositely arranged in both end portions of the U-type arm 111.
The separated holding devices shown in FIG. 2A have a low degree of freedom of positioning as mentioned above. Therefore, a device having an .OMEGA.-type arm having an .OMEGA.-character shape is used in many cases instead of the separated holding devices having the U-type arm.
In the conventional holding device for a circulatory organ, the X-ray detecting portion (I.I., an optical system, a TV camera, etc.) and the X-ray generating portion 104 as heavy objects are arranged in both end portions of the C-type arm 103 so that rotating inertia of the holding device is large. Further, the C-type arm 103 has an asymmetrical shape so that it is difficult to balance rotation of the C-type arm 103. Accordingly, positioning control of the holding device is electrically performed. However, a judgment about how to operate the holding device must be made to set desirable positioning. Further, skill is required to precisely perform an operation corresponding to each positioning and it is difficult to make a fine adjustment. Accordingly, it is difficult to accurately control the operation of the holding device in intended positioning.
It may be considered that this problem is solved by arranging a counterweight on the C-type arm 103, etc. to balance the rotation of the C-type arm 103, etc. so as to manually operate the holding device thereby making the fine adjustment of positioning by this manual operation. However, in this case, the rotating inertia of the holding device is increased so that there is also a fear that it is difficult to accurately set the desirable positioning.
It may be further considered that a solid state detector (a plane detector) formed by plural solid state image pickup elements is used as the X-ray detecting portion instead of an image intensifier (I.I) to facilitate the manual operation so as to make the holding device compact and light in weight. However, when this plane detector is used, the holding device is unbalanced in weight on the side of the X-ray generating portion 104 so that the moment of rotational inertia of the holding device is greatly increased in comparison with the present situation and there is also a fear that it is difficult to control the operation of the holding device.
The conventional separated holding devices can make only the oscillating movement, the horizontal movement and the vertical movement of the X-ray generating portion 124 (or the X-ray detecting portion 125). Therefore, the X-ray generating portion 124 (or the X-ray detecting portion) cannot be arranged under a subject. Accordingly, a problem exists in that an application range of the holding device is extremely limited (limited to an use as a lateral positioner of a biplane radiography).